This invention relates to photographic processing apparatus and is more particularly concerned with the processing of photographic materials using low volumes of processing solution.
Rotating drum arrangements are well-known for the processing of photographic material. U.S. Pat. No. 4,613,223 discloses an arrangement in which a flexible sheet of photographic material is driven along an endless curved path within a processing tank by passing the sheet through nips formed between at least one pair of driven rollers. At least one of the driven rollers is the drum itself. During processing, the emulsion (sensitive) surface of the sheet is arranged not to come into contact with any stationary part of the processing vessel as it is being processed. This prevents damage to the surface during processing. After driving the sheet around the endless path for a predetermined number of cycles, which defines the processing time, the sheet is then directed out of the processing tank.
The arrangement described above, has the disadvantage that little or no agitation is applied to the emulsion surface of the photographic material being processed. This may result in uneven processing of the material and variable sensitometry.
It is known to provide rotating drum arrangements in which a secondary oscillatory motion is applied to the drum to improve agitation of the processing solutions.
U.S. Pat. No. 4,302,092 discloses a hollow rotating drum mounted in a support in which material to be processed is placed with processing solution inside the drum. The drum is axially slidable relative to the support and is driven by a hand crank against the action of a soft spring. During rotation of the drum, it is displaced axially relative to the support against the soft spring to cause the processing solution inside the drum to oscillate axially.
U.S. Pat. No. 3,981,488 discloses an arrangement in which a hollow cylindrical processing tank is mounted on a support for rotation. A disc is eccentrically mounted on a drive shaft at one end of the support to provide a vertical oscillating motion to the tank at one end.
U.S. Pat. No. 3,977,876 discloses a rotating drum arrangement in which oscillatory motion is provided by the engagement of an oblique slot with a roller or a circumferential rib, the slot either being carried by the drum itself or by the base on which the drum is mounted. In either case, an axial oscillatory motion is applied to the drum as it is rotated.
U.S. Pat. No. 3,595,156 discloses an arrangement in which film to be processed is held inside a vat surrounding a cylinder. The cylinder has ribs formed on its surface to provide agitation to the processing solution in the vat. The cylinder may be driven in at a predetermined uniform cyclic speed or can be over variable speed either in one direction or reversible directions.
U.S. Pat. No. 3,550,521 discloses a hollow cylindrical processing tank which oscillates about its axis between a first and a second position to effect processing of the photographic material placed inside the tank. The tank can then be moved to a third position where the used processing solution is drained from the tank.
The oscillating arrangement disclosed in U.S. Pat. No. 3,550,521 has the disadvantage that relatively large volumes of solution are required. This makes this particular arrangement unsuitable for unstable and/or single use processing chemistry.
Co-pending British Patent Application No. 9125297.3 (now published International Patent Application No. W093/11464) discloses a rotating drum arrangement in which low volumes of processing solutions are used allowing unstable and single use chemistry to be efficiently used.